With the increasing concern for safety, there is a positive move towards providing safe materials for public and household use. One particular area of need is that of providing flame resistant or flame retardant products for use by the ultimate consumer. As a result of this demand, many products are being required to meet certain flame retardant criteria both by local and federal government and the manufacturers of such products. One particular set of conditions employed as a measuring standard for flame retardancy is set forth in Underwriters Laboratories, Inc. Bulletin 94. This Bulletin sets forth certain conditions by which materials are rated for self-extinguishing characteristics.
It is known to use organopolysiloxane in admixture with polycarbonates to provide a composition having good mold release properties from U.S. Pat. No. 2,999,835. Also, U.S. Pat. No. 3,087,908 discloses resinous material comprising organosiloxane in admixture with polycarbonates, which composition facilitates the formation of clear films which are free from blemishes, undesirable color effects, bubbles, and craters.
However, none of the above references disclose that when a minor amount of a particular organopolysiloxane polymer is mixed with a thermoplastic polymer and a flame retardant additive, the thermoplastic polymer is rendered flame retardant.
The organopolysiloxane polymer additive is able to stop the dripping of molten, flame particles from burning thermoplastic parts. In the case of self-extinguishing polymers, these materials can be ignited and do burn as long as the ignition source is present but extinguish themselves within a few seconds after its removal. However, during the burning period, before flame-out, the self-extinguishing polymer tends to drip molten flaming fragments which will ignite other material situated below the first fire. Howvever, the instant additive in admixture with the aromatic polycarbonate prevents this dripping of molten, flaming particles.